Light lock for air ionizer to shield photosensitive material



5, 1968 T. c. WHITMORE ETAL 3, 0 ,76

LIGHT LOCK FOR AIR IONIZER TO SHIELD PHOTOSENSITIVE MATERIAL Filed April 3, 1967 2 Sheets-Sheet l THOMAS C WH/TMORE PETER H. ZACHMA/V/V INVENTORS' g aw AGENT 1968 T. c. WHITMORE ETAL LIGHT LOOK FOR AIR IONIZER T0 SHIELD PHOTOSENSITIVE MATERIAL 2 Sheets-Sheet 2 Filed April 3, 1967 THOMAS C WH/TMORE PETER H. ZACHMA/V/V INVENTORS AGE/VT United States Patent 3,409,768 LIGHT LOCK FOR AIR IONIZER T0 SHIELD PHOTOSENSITIVE MATERIAL Thomas C. Whitmore and Peter H. Zachmann, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Apr. 3, 1967, Ser. No. 627,990 13 Claims. (Cl. 250 -49.s

ABSTRACT OF THE DISCLOSURE A device for shielding the surface of a photosensitive material from any irradiation generated by a corona discharge means. The device is adapted to be positioned on the discharge end of the corona discharge means and 18 provided with a passageway that converges in one direction and connects the discharge opening to an orifice CllS- placed from the opening by a distance sufiicient to provide a shielding effect.

Field of the invention Background of the invention The use of gas ionizers for charging or discharging the surface of a web or sheet of material is well known. Such gas ionizers direct a flow of ionized gas toward a surface of a web to remove any electrostatic charge thereon or to place a charge of a particular polarity on the surface. In the manufacture of photosensitive materials, it is essential that the material not be exposed to any irradiation including that generated by a corona discharge means. While it is necessary to remove any static electricity from a web of photosensitive material to facilitate winding, cutting and packaging, etc., of the material, any corona irradiation incident on the material causes fogging streaks which result in portions of the material so exposed being rendered unusable. Consequently, in treating photosensitive materials, any device that is used to alter the electrostatic charge on the material must be one which does not fog the material and one whose efficiency is not substantially reduced by the addition of any means that might be used to shield the photosensitive material from such irradiation.

Summary of the invention One object of the present invention is to provide an efiicient light lock for a corona discharge means which shields a photosensitive material being treated thereby from irradiation generated by the corona discharge means.

Another object of the invention is to provide a device which can be used as a part of a corona discharge means, when treating a photosensitive material, to prevent irradiation from damaging the material.

A further object of the invention is to provide an air ionizing device with a member having a passageway which displaces the flow of ionized air to a photosensitive material so that the material is shielded from any irradiation generated by said device.

A still further object of the invention is to provide a device receivable by a corona discharge means which is capable of converting a flow of ionized gas to a substantially narrow diverging stream and which displaces the flow of ionized gas so as to shield the photosensitive material being treated from any irradiation generated by the corona discharge means.

Other objects of the invention are to provide a device that is capable of being used with a corona discharge means which is simple in construction, is highly eflicient in operation, and does not materially reduce the efiiciency of the corona discharge means.

The aforementioned objects of the invention are attained by a device that is securable to and extends from a housing in which a corona discharge means is arranged. The housing is provided with an opening through which a uniform flow of ionized gas is applied to a surface of the material being treated. The device comprising the invention is applicable to a cylindrical type of corona discharge means having only a small discharge opening, or to an elongated type of corona discharge means having an opening which extends transversely of the width of the material to be treated. In either case, the device is secured to the end of the housing facing the photosensitive material and is provided with a passageway that is generally convergent in at least one direction and can also be generally divergent in the other direction, the passageway being obliquely coextensive with the opening in the corona discharge means and terminating in an orifice that is in spaced relation to the surface of the material and displaced from the opening in the corona discharge means by a distance sufficient to shield the material from any irradiation generated by the corona discharge means. The passageway can be one that is continuous and uninterrupted or can comprise several parts that are coextensive with each other and inclined at an acute angle to each other and relative to the axial plane of the opening in the corona discharge means. The acute angle is such that each part acts as a light lock against any direct irradiation. The passageway progressively decreases in at least one dimension between the junction of the opening and the passageway and terminates in a narrow orifice at the discharge end of the device. The efliciency of the light lock comprising the invention is increased considerably by providing an aperture which connects the passageway to the ambient pressure, thereby reducing turbulence and any Bernoulli effect in the passageway. While the device is described hereinafter as being used for removing or substantially altering electrostatic charges on a web of photosensitive material, it can also be used with any web or sheet of dielectric material in which a stream of ionized gas is to be applied to a surface of the material to alter any electrostatic charge thereon.

The term alter or altering as used in this specification and in the claims is intended to include any one of the following conditions:

To remove (neutralize) the charge (negative or positive) on a web or sheet;

(2) To change the charge on a web or sheet from negative to positive, or vice versa;

(3) To increase or to decrease the charge (negative or positive) on a web or sheet; and

(4) To place a charge (negative or positive) on an uncharged web or sheet.

The term applied to is used in this specification and in the claims to define a flow of gas directed normal to, at an angle to, or over and across a surface of the materia The term corona discharge device or means is used in this specification and in the claims to define a selfsustaining electrostatic discharge device for generating positive and/or negative ions in accordance with the applied current. With alternating current applied to the corona discharge device, positive ions will be generated 3 on the,;positive halfof the cycle, whereas, negative ions will be generated on the negative half. With direct current, positive or negative ions will be generated in accordance with the direction of current flow in the needle.

Description of the drawing Reference'is now made to the accompanying drawings in which like reference numerals designate like parts and wherein: I, f

FIG. 1 is a schematic perspective view showing an ar rangement of a plurality of ionizers with light locks se cured thereto arranged transversely on one side of a mov ing web of photosensitive material;

FIG. 2 is a schematic perspective view similar to FIG. lin which a corona discharge means having a slit extending transversely of a moving web of photosensitive material is arranged on one side of the web;

FIG. 3 is a vertical section through a corona discharge device such as that shown in FIG. 1 with a light lock secured to the end thereof;

FIG. 4 is a perspective'view of a preferred form of light lock showingparticularly the structure for forming a diverging passageway therein;

FIG. 5 is a perspective view of one of the complementary portions of the light lock shown in FIGS. 3 and 4 and disclosing particularly the surfaces that cooperate with those of the other portion shown in FIG. 4 to provide a diverging passageway; and

FIG. 6 is an end view of the main portion of the light lock member shown in FIG. 4 with the cooperating member being indicated by dotted lines.

Description of the preferred embodiments of the invention With particular reference to FIGS. 1 and 2, a web or strip 10 of photosensitive material is moved continuously, by means not shown, past a plurality of corona discharge means 11 or a corona discharge device 12 as shown in FIG. 2. While the invention is described hereinafter with reference to a web 10, it is also applicable to sheets of material which are moved successively past the corona discharge means 11 or 12. The devices 11 and 12 can be arrangedrelative to either side or both sides of the moving web 10 and, in the latter case, can be arranged either opposite one another, or spaced from each other longitudinally of the web. If the web 10 is relatively wide, then a plurality of the corona discharge devices 11 can be arranged transversel of the web with their streams of ionized air slightly overlapping in order to insure full coverage of the width of the web.

The corona discharge device 11 comprises a housing 15 having a circular recess 16 and a coextensive, threaded opening 17. The housing 15 is made preferably of an insulating material, such as a plastic or ceramic material, and is provided with a recess 16 which surrounds a needle 18 that is mounted in housing 15, said needle extending beyond the end of the housing 15 with its point positioned as shown in FIG. 3. The mounting end of needle 18 is connected in a known manner to a source of potential by means of a lead 19. The housing 15 is also provided with a threaded opening 20 which receives a connector 21 to which a tubular member 22, preferably of a flexible material, is connected for introducing a pressurized gas, such as air, into the recess 16. The threaded opening 17 receives a metallic sleeve 23 in which a plate 24 having a small opening 25 is retained against movement in one direction by a spring ring 26. A thin metallic sleeve 27 is arranged between the ring 26 and plastic sleeve 28 which is provided with a plurality of openings 29 sur' rounding an opening 30 through which the needle 18 ex tends. When threaded end 31 of sleeve 23 is seated in the threaded opening 17, the sleeves 27 and 28 retain plate 24 against ring 26. The air introduced into recess 16 moves through the openings 29 and through the opening 25, being ionized by the portion of needle 18 within sleeve 27 when a potential is applied to said needle. Normally, for any dielectric material other than a photosensi tive material, the end 32 of sleeve 23 is positioned relative to the surface of web 10, so as to alter its surface charge in accordance with the potential applied to needle 18, in a known manner. 7

In order to shield the surface of the photosensitive material from anyirradiation generated by the corona discharge means 11, a light lock, generally designated by the numeral 35' comprises a cylindrical member or portion 36 and a member 55, the member 36 being secured to the end 32 of sleeve 23. The members 36 and 55 can be made of an insulating material if an AC potential is applied to needle 18 or can be made of a partially conducting material if a DC potential is applied to the needle. The cylindrical member or portion 36 is provided with a recess 37 for receiving the end 32 of sleeve 23 and is retained in position thereon by means of a set screw 38 or a similar fastening means. With reference to FIGS. 3 and 4 the cylindrical portion 36 is formed with :an extension 39 substantially as shown'in FIG. 4. The extension 39 is provided with a surface 40 that is sepa rated by a pair of spaced ribs 41,42 which extend from the surface of wall 43 to the free end 44 of the light lock 35. The wall 43 is provided with an opening 45 which is aligned with the opening 25 in plate 24 and, in effect, forms a continuation of opening 25 when the light lock 35 is positioned on corona dischargemeans 11. The inner surfaces 46, 47 of each of the ribs 41, 42 diverge from the plane of wall 43 to the end 44. The inner surfaces of ribs 41, 42 form the extremities of a plurality of surfaces 50, 51 and 52 which coextend from wall 43 to end 44. As viewed in FIG. 4, the surface is substantially parallel to a horizontal axial plane through the opening 45 and is tangent to the periphery of said opening. Surface 51 is coextensive with surface 50 and inclined at an acute angle thereto toward end 44. Surface 52, in turn, is coextensive with surface 51 and also inclined at an acute angle toward end 44 and relative to surface 51. A member 55, as shown in FIGS. 4 and 5, is provided with a pair of diverging recesses 56, 57 which are of a size and shape so as to be receivable by ribs 41, 42. The portion 58 intermediate recesses 56, :57 is provided with a plurality of surfaces 59, 60 and 61. The aforementioned surfaces are inclined at acute angles relative to each other such that when member is positioned on extension 39 to complete light lock 35, the inclined surfaces 50 and 51, 52 and 59, and and 61 cooperate, respectively, to form a converging passageway 62 between opening 45 and end 44. Also, with reference to FIG. 3, it will be noted that the extension of surface 51 will intersect wall 43 above aperture 45 and the extension of surface 52 will intersect surface 60 at about its midpoint. At a result, each of the sections of passageway 62 formed by surfaces 51, 60 and 52, 61 form individual light lock sections, the angles of inclination of these surfaces being such as to produce this effect.

The passageway 62 is generally divergent from the opening 45 to the end 44 due to the diverging inner surfaces 46, 47 of ribs 41, 42. Therefore, passageway 62 progressively increases in width from opening 45 to end 44. As shown in FIG. 4, the dotted line 63 indicates the position along each of ribs 41, 42, that the surfaces 61, 60 and 59 assume when member 55 is in assembled relation with extension 39. It will be noted that the angular relationship of the inclined surfaces is such that the height of passageway 62 decreases progressively from opening 45 to end 44 and terminates in a relatively narrow orifice or slit 64 at the end 44. Due to the inclination of the surfaces 50, 51 and 52 of the extension 39 and surfaces 61, 60 and 59 of member 55, orifice 64 is displaced relative to opening 45 and opening 25. This displacement is, and must be, sufiicient so that any irradiation generatedby the corona discharge device 11 is prevented from being seen by the photosensitive material. In order to eliminate any reflection of such irradiation from one surface to another, the inclined surfaces of extension 39 and member 55 can be sand-blasted, covered, painted with a dull black, non-reflecting material or treated in any other manner to eliminate any reflection from said surfaces.

The efficiency of an ionizer using a light lock is reduced when the ionized gas is converted from a circular flow. (openings 25 and 45) to a rectangular flow of gas (passageway 62). However, more useful distribution of the ions occurs because of the shape of the orifice 64. Gas pressure also influences the efficiency because of the turbulence created by passage of the gas through opening 45 by which the ionized gas is introduced into passageway 62. Such turbulence can be decreased and, hence, an increase in efiiciency can be accomplished by providing at least one breather hole 65 in extension 39, as shown in FIGS. 3 and 4, and/or in member 55. The breather hole 65 is positioned immediately adjacent opening 45 and connects the passageway 62 to ambient pressure. Breather hole 65 allows air to enter the passageway 62 and decreases any Bernoulli etfect as well as any turbulence by relieving the Venturi effect of opening 45 jetting the ionized gas into the passageway 62. Such a breather hole materially increases the efiiciency of the ionizer unit. In one case, by actual measurement, it Was found that the efiiciency was increased from 23% (without the breather hole) to about 83% of the original efiiciency with such holes.

With reference to FIG. 2, the diverging passageway of the light lock described hereinabove is also applicable to an ion generator of more than one ionizer within a single chamber. A multiple needle ionizer, such as shown in FIG. 2, is described in detail in U.S. patent application, Serial No. 469,157, filed July 2, 1965, in the name of Thomas C. Whitmore. In this embodiment, the light lock 70 is secured to the end of the corona discharge device 12. The light lock comprises a member 71 that is secured to the walls of corona housing 72 by any suitable means, the housing being provided with an elongated opening 73 and with a plurality of needles 80 which extend from the rod 81 toward opening 73, as described in the aforementioned application. Member 71 is provided with a passageway 74 that is coextensive with the opening 73 in one direction and obliquely coextensive in the other direction. The passageway 74, as disclosed in FIG. 2, comprises two coextensive sections 75 and 76, the surfaces of which are inclined at acute angles relative to opening 73 and to each other so that passageway 74 converges from openings 73 to the end 77 of member 71 at which it forms a relatively narrow orifice 78.

As described above, the inclination of sections 75 and 76 is such that each section serves in itself as a light lock against direct irradiation. Also, the inner surfaces of each section can be treated as described above to reduce as much as possible any reflected irradiation.

In this embodiment, the height of passageway 74 progressively decreases from opening 73 to orifice 78. The orifice 78 at the end 77 of member 71 must be displaced from opening 73 by the inclination of sections 75 and 76 by a distance sufficient to shield the photosensitive material from any irradiation generated by the corona discharge device 12.

As in the embodiment disclosed in FIGS. 3-5, member 71 is provided with at least one breather hole 82, the number of such holes being dependent on the length of opening 73 and the amount of turbulence. The breather hole 82 is arranged close to opening 73 and connects passageway 74 to ambient pressure.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim: 1. Apparatus for altering the electrostatic condition of a photosensitive material including a housing having a chamber connected to a source of pressurized gas and at least one opening through which a uniform flow of said gas is applied to a surface of said material, and corona discharge means within said chamber and connected to a source of potential for generating an ionized zone between said opening and said surface; the improvement which comprises:

means securable to and extending from said housing with the free end thereof adjacent said surface and provided with a generally convergent passageway obliquely coextensive with said opening and terminating at said free end in a narrow orifice;

said orifice being displaced from said opening in a direction and by a distance suflicient for shielding said material from any irradiation generated by said corona discharge means.

2. Apparatus in accordance with claim 1 wherein said passageway is generally rectangular in cross section and progressively decreases in at least one dimension between the junction of said opening and said passageway and said orifice.

3. Apparatus in accordance with claim 1 wherein said passageway comprises a first part coextensive with said opening and inclined at an acute angle relative to the axial plane of said opening and a second part coextensive with and inclined at an acute angle relative to and in the same direction as said first part.

4. Apparatus in accordance with claim 1 wherein said last-mentioned means is provided with at least one opening intersecting said passageway adjacent said opening for connecting said passageway to ambient pressure for decreasing turbulence in said passageway.

5. Apparatus for altering the electrostatic condition of a photosensitive material including a housing having a chamber connected to a source of pressurized gas and at least one opening through which uniform flow of said gas is applied to a surface of said material, and corona discharge means within said chamber and connected to a source of potential for generating an ionized zone between said opening and said surface; the improvement which comprises:

means securable to and extending from said housing with the free end thereof adjacent said surface and provided with a generally divergent passageway obliquely coextensive with said opening and terminating at said free end in a narrow orifice for converting said ionized zone to a substantially narrow diverging stream extending transversely of said material;

said orifice being displaced from said opening in a direction and by a distance sufficient for shielding said material from any irradiation generated by said corona discharge means.

6. Apparatus in accordance with claim 5 wherein said passageway is generally divergent from said opening to said orifice in one direction and generally convergent from said opening to said orifice in the other direction.

,7. Apparatus in accordance with claim 5 wherein said passageway is generally rectangular in cross section and progressively decreases in one dimension and progressively increases in the other dimension between the junction of said opening and said passageway and said orifice.

8. Apparatus in accordance with claim 5 wherein said passageway comprises a first part substantially normal to the junction plane of said passageway and said opening and intersecting the latter, a second part coextensive with and inclined at an acute angle relative to said first part,

and a third part coextensive with and inclined at an acute angle relative to and in the same direction as said second part.

9. Apparatus in accordance with claim 8 wherein each part of said passageway is rectangular in cross section and progressively decreases in one dimension and progressively increases in the other dimension between the junction of said opening and said passageway and said orifice.

10. Apparatus in accordance with claim 5 wherein said converting means is provided with at least one opening intersecting said passageway adjacent said aperture for connecting said passageway to ambient pressure for decreasing turbulence in said passageway. I

11. A device for converting a flow of ionized air being discharged through an opening in the end of an air ionizer and applied to a surface of a photosensitive material to a relatively narrow stream of ionized air and for shielding said material from any irradiation generated by said ionlzer comprising:

a first member having a first portion provided with an aperture alignable with said opening, when said member is positioned on the end of said ionizer with the free end of said member adjacent said material, and a second portion extending from said first portion and having a surface intersecting said aperture and obliquely inclined from the latter toward the end of said first member; a

a pair of spaced walls extending from said surface with at least the inner surfaces thereof diverging from said aperture to the end of said second portion;

a second member securable to the second portion of said first member and having an obliquely inclined to said first planar surface.

surface cooperating with the obliquely inclined'sur face of said 'second portion to form a diverging passageway of decreasing height from said'opening to the end of saidsecond portion at which saidpassage way terminates in a narrow orifice that is displaced from said opening by a distance 'sufiicient to shield said material. j

' 12. A device in accordance with claim 11 wherein said surface of the second'portion of said first member-and said surface of *said second member'each comprises at least two coextensive planar surfaces, thefirst pla'nar 'sur face being inclined at a' first acute angle relative to an axial plane intersecting said opening "and the second planar surface being inclined at an acute angle relative 13. A'device in accordance with claim 11 wherein one of saidsecond portions and said second member are provided with at least one openingintersectingsaid passageway adjacent said aperture for connecting said passageway to ambient pressure for decreasing turbulence in said passageway. I Y I a No referencescited.

WILLIAM F. LINDQUIST, Primary Examiner. i I 

